The invention relates to nematic liquid crystals in electro-optical components for the modulation of transmitted or reflected light, as well as for the display of figures, symbols and images, and to a method for the production of these new substances.
Liquid crystals, particularly the ones of the nematic type, are personified by anisotropy of optic, dimagnetic and electric characteristics. Because of these characteristics, nematic liquid crystals are successfully used in the manufacture of electro-optical components for the modulation of light, as well as for display of figures, symbols and images. Such components are extremely suitable as displays for electronic clocks, computers and other micro-electronical products.
New and increasingly higher demands are placed on the liquid crystal substances in displays to be used in modern devices, with the specific characteristics of these substances critically influencing the characteristics and application ranges of the displays. Since no pure compound exists which comes even close to meeting all the demands, mixtures of several compounds are almost always used. The characteristics of the mixtures are, to a large extent, determined and influenced by the individual mixed components. For the adjustment of the mixtures to all possible applications, many individual components of various categories of substances, with quite specific characteristics, may be needed. Besides substances with low melting temperatures and sufficiently high clear temperatures, substances with very low birefringence are needed, for example, in the case of new variations based on the Schadt-Helfrich-effect (twist cells). (G. Baur in: The Physics and Chemistry of Liquid Crystal Devices (1980), edited by G. J. Sprokel, Plenum Publ. Corp. New York 1980, p. 61).
The previously known dioxane derivatives have undesirably low clear points in part, or exhibit an undesirable tendency to forming smectic phases (e.g., the 5-n-alkyl-2-cyanophenyl-1,3-dioxane, WP 139852 and WP 139867; additionally, substituted cyclohexyl-dioxane, WP CO 9 K/232 636/0).
It is the object of the invention to provide new nematic liquid crystals with favorable physical characteristics, particularly regarding the melting- and clear temperatures, stability against thermal stress, light, and electrical fields, as well as low birefringence, as well as to provide a method for the production of these substances.